Pump and motor



Sept. 9, 1952 c. s. PRENDERGAST ETAL 2,609,754

PUMP AND MOTOR Filed Sept 21, 1951 4 Sheets-Sheet l dd M Arron/vsp Sept- 9 1952 c. s. PRENDERGAST ET AL 2,609,754

PUMP AND MOTOR Filed Sept. 2l, 1951 4 Sheets-Sheet 3 /f nu fr Paar dri* 6x0" 'ATTORNEY Sept. 9, 1952 c. s. PRENDERGAST ET AL 2,609,754

PUMP AND MOTOR Filed sept. 21, 1951 4 sheets-sheet 4 dU- 7ATTORNEY Patented Sept. 9, 1952 :PUMP AND Moron Charles Scott Prendergast, Eashing,

Richard Samuel Prendergast, Elstead, Godfrey William Beaumont Dixey, London, and Hamilton Gordon, Elstead, England Application September 21, 1951, Serial No. 247,712

In Great Britain September 14, 1948 (Cl. S- 4) 4 Claims.

Our invention relates broadly to pumps and motors and more particularly to an improved rotary pump or motor of the kind having a series of stator chambers, a series of phase-displaced rotors one in each stator chamber, and movable abutments between the stator chambers and the rotors, and wherein the stator chambers and the rotors are relatively profiled to bring about reciprocal rates of acceleration and deceleration of the movable abutments as the rotors rotate, whereby the total instant fluid displacement of the series is practically uniform.

This application is a continuation-in-part of our application Serial No. 99,702, iiled June 17, 1949, now abandoned for Improvements Relating to Pumps and Motors.

One of the objects of our invention is to provide a construction of rotary pump or motor having a high degree of efficiency and reliability.

Another object of our invention is to provide a construction of rotor for rotary pump or motor which is formed on predetermined contours including interconnected curves, one portion of which operates in coaction With associated parts of the rotor pump or motor at a constant rate of acceleration and another portion of which operates in association with the said parts of the rotary pump or motor at a constant rate of deceleration.

A further object of our invention is to provide a new and improved rotary pump or motor, of the movable abutment type, comprising a series of stator chambers with a series of rotors phase-displaced at 90 degrees, there being one rotor to each stator chamber, and two movable abutments, diametrically opposed, contained between each stator chamber and rotor, inlet and dischar-ge ports on either side of each abutment being isolated from each other by sealing contact of the abutments with the stator and rotor.

Other and further objects of our invention reside in the construction of a rotor for a rotary pump or motor, the contour of which is precalculated according to mathematical formulae for insuring mass production of the rotors at relatively low cost and for obtaining reliable and uniform operation of pumps or motors in a large production program as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which;

Figure 1 is a vertical longitudinal sectional View through a fragmentary portion of a multiple chamber pump embodying our invention, the view being taken on line I-l of Fig. 2; Fig. 2 is a transverse sectional view taken on the line II--II of Fig. 1; Fig. 3 is a transverse sectional view taken on line III-III of Fig. 1; Fig. 4 is a fragmentary longitudinal sectional view taken on line IV-IV of Fig. 2; Fig. 5 is a fragmentary longitudinal sectional view taken on line V-V of Fig. 2; Fig. 6 is a View of one of the identical rotors in the `rotary pump or motor in our invention; Fig. 7 is a curve diagram illustrating thecompounded flow displacement controlled by the rotors of the rotary pump or motor illustrated in Figs. l-6; Fig. 8 illustrates a modified form ofrotary pump or motorembodying our invention in which the abutments in one stator chamber are connected to aligned abutments in the other stator chamber through lever members for controlling the mutual coaction thereof; Figs. 8a and 8b are perspective views showing the shape of the levers and abutments used in the structure of Fig. 8; Fig. 9 shows the coaction of one of the abutments with the rotor of the pump where the minor circular arc of the rotor is in contact with the sliding abutment; Fig. 10 shows the condition where the major circular arc of the rotor is in contact with the sliding abutment; Fig. 11 shows the condition in which the sliding abutment is in contact with the curves of the rotor intermediate the major and minor circular arcs thereof; and Fig. 12 is a diagram showing the manner of laying out the curve contours forthe rotor in accordance with the principles of our invention.

Referring to Figs. 1 to 6 reference character I indicates a shaft journalled in end housings 2 and 3 of the fluid casing, the shaft having keyed thereontwo similar rotors 4 (of special profile hereinafter particularly described) phase-displaced at degrees and surrounded by stator elements 5. Spacer plate 6 separates on stator and rotor from the other stator and rotor while the housing members, which include liners 1, contain them at the ends. The described parts are held assembled by bolts 9, shown in the cross sectional views Figs. 2 and 3, but omitted from the longitudinal sectional views for the sake of clearness, which pass through holes formed through the end housings 2, 3, the liners 'l and stator element 5, and the spacer 6. The bore of each stator element is cylindrical in shape.

Each of the two stator elements has two diametrically opposed abutments l0 which slide in radially extended recesses Il in the stator elements, the recesses in one stator coinciding radially and circumferentially with the recesses in the other stator and disposed in a plane extending through the shaft I. The outer ends of the recesses in one stator are connected to the outer ends of the recesses in the other stator by means of holes IZA through the spacer member Slots I2 in the rear of the abutments connect the outer ends of kthe recesses to the bore of the stator. These sliding abutments bear constantly on the perimeters of the rotors under iiuid pressure on their outer end surfaces. Owing to the special form of the phase-displaced rotors the iluid pressure remains constant as the fluid displaced by one pair of abutments moving outwards is at all times exactly absorbed by the aligned pair of abutments moving inwards, by means of holes IZA 1nk the spacer plate E3. Initial pressure at the outer ends of the abutments is obtained through slots I2 in the rear of the abutments Ill. slots I2 can be omitted as initial pressure Vcan be obtained through the sliding clearance allowed for the abutments in the recesses.

Extending diametrically into the end housing member 3 isa fluid inlet duct-.I3 shown more par-A ticularly in Figs. Zand Zlu'rhich communicates with two sets of aligned holes inthe said end member 3, the liner l,'thel stators and the spacers 6, these aligned holes forming two diametrically op posed-fluid inlet passages Ill each of which opens radially` intothe stator chlambersiin advance of theslidingfabutments inlrespect tothe rotation of the shaftl. `also extending diametrically into thevhousi'ng member 1%as shown in Figs. 2 and 5, isa iiluidfdiscnarge duct I which communicates With'two diametricallyroppos'e'd uid outlet passages I each of which vcommunicates radially with the stator chambers in the rearoi thev sliding abutments.

It will be understood that since eachrotor #l coacts with two sliding abutments lll, each of which is disposed between a luid inlet I4 and a iiuid outlet It; two identical displacement capacities are afforded in each stator, each of which capaci`- ties is swept twice during onev revolution of the rotor. Such an arrangement has the advantage thatlit-.automatically provides hydraulic balance of each-,rotor and consequently7 of the driving shaft.. y Y

Thefperimeter Vof each rotor is `formed by a major and aminor pair of diametricallyopposed arcs, as shown-at a and b in Figy, all arcs-'being subtended loy` equal angles of less than V90 degrees, and the chords of the pair of major yarcsbeing disposed at 9i) degrees ,to the chords of the pair of minorarcs. Four joining curves c, connecting adjacent major and minor arcs a. and b and forming ya smooth junction `'with each arc, complete theperimeter. The radii 'of the major arcs are eachalmost equal to the radius` of the stator chamber, thediiierence between them being suicient to allow for running. clearance. The radii of the minor arcs are smaller than the radii oi the major arcs by a predetermined amount, this amount being a governing factor in the cubiccapacity of the pump o'r motor. The radius of a joining Ycurve at thepoint mid-way between adjacent majorrand minorV arcs is the mean of the radius ofthe major arc and the radius or the minor are. Thel radii of the remainder of the joining curve can be .determined as follows: The difference between the radius of a major arcand any radius of the joining curve between the adjacent end of the major arc and the mid-way point of the. joining curve varies with the square of the angle contained between the radius and the junction point of the joining curve and the major are. For exampleif this difference is D at one degree from the end of the major arc, it

If desired l bers For example*if this difference is d at one degree from the end of the minor arc, it should be 4 d at two degrees from the end oi the minor arc and 9 d at three degrees from the end of the minorarc. If this is followed in proiiling the rotors 4, the abutments iii in contact with the rotors will travel outwards for the iirst hali or their movement at a constant rate of acceleration andfor the second half of their movement at a constant rate of deceleration. During the same periods the aligned abutments in contact with theother rotor will travelinwards for the lirst half of Vtheir movement at a constant'rate of acceleration and for the second half of their move ment at a constant rate of deceleration. These exactly reciprocal rates of movement determine thatl the fluid displacement of an abutment when movlng outwards is at all times equal to the fluid absorption of an `abutmentmoving inwards, thus ensuring continuous contact at all times between the abutments and the rotors. Having provided continuous Contact between the abutments and the rotors by this form of prole it is found that the combined instant displacement produced by rotation of the two complementary rotors is practically constant.

Fig. 7 shows the characteristic curves for the compounded ow of two coacting rotors. In another. form of our invention as shown in Fig. 8 we have shown a modified assembly including housing members .2 and 3f in which shaft I is journaled and wherein the abutments til in one stator chamber 5 are connected to the aligned abutments I D. in the other stator chamber 5" by levers I8 which are arranged to pivot halfway between the abutments in the spaceiplate Gf. The shape of 'levers i3 is illustrated more clearly in Fig. 8a and the shapev of each abutment is shown in Fig. Sb.

lIn order that this arrangement can operate with the abutmentsheld positively in continuous Contact with the rotors Il andl 4 by means of .the pivoted levers I8, it is essential that the joinmgV curves connecting the major and minor arcs should give reciprocal rates of acceleration and deceleration to the abutments. rIhis is ensured byv the rotor construction previously described. If desired the fulcrums I9 of the levers ISmay be. made adjustable by screw threads or other sultable means formed in spacer plate 6 to bring the abutments into contact with the rot-ors Il' and e rIfhespacer plate 6 is apertured at 6 to enable the levers I 8- to pass laterally therethrough for engaging opposite ends of abutments IBY and Ill in the adjacent lstator chambers so thatl the abutments are alternately displaced The fulcrums IB for the levers I@ are adjusted adrally in ttlllie spacer plate il through micromeer screw reads I9 en a e e 1' threads in the spacer plaegl.D mamma sclew crurns I3 have been set in the desired position for pivoting the levers iii on the pivot points I9 which fit into recesses i3 in leversy I8 the fulcrumsV are locked in position by screw iremfvvhich engage the screw threaded er1-ds n.' 1. 1 ISB oL the fulci ums IS for selectively setting the When the fulfulcrums in a predetermined position."` Adjustment may bemade ofthe positions of the fulcrums for obtaining most `eilicient results. Again, the fulcrums'may be resiliently mounted on springs or rubber blocks to provide tolerances and allow for any inaccuracy in Athe manufacture. p Alternatively-the levers t8 themselves may be in the form of flat springs. It must be understood that the mechanical interconnecting of the abutments may be used inl conjunction with the hydraulic interconnecting ot the abutments already described. p p

The contour of `the abutment face in contact with the rotor is. very important. Figs. 9-11 show the various.l conditions encountered in the operation of a pump or motor embodying our invention and Fig. 12 shows the manner of laying out the contour of the rotor. On account of the varying rotor prole only line contact is possible andit is `essential that this line of contact must remain practically constant in relation to the abutment face. 'If the line of contact were allowed to travel backwards and forwards across the abutment; face it would upset the reciprocal rates of acceleration and deceleration of the abutments and it would then become impossible `to maintain continuous contact between the abutments and the rotors as illustrated for example in Fig. 9. Because reciprocal rates of acceleration and deceleration, govern Vthe movements of the abutments it follows that the total cubic capacity of the combined spaces at the outer ends of the abutments remains practically constant. The pressure in these spaces must inevitably build up to approximately the pump delivery pressure and this pressure is felt over the areas of the outer faces of the abutments forcing them against they rotor. If there were no reaction to this pressure excessive wear would take place between rotors and abutments at high hydraulic pressures. By arranging the contour of the inner face of an abutment l0 so that the line of Contact Illa is close to that `face which is adjacent to the inlet porting I4 of the pump, a reactive pressure is exerted on the abutment which reduces the resultant pressure between the abutment and the rotor t0 a minimum as represented in Fig. 9.

Another importantfeature of our construction deals with those portions of the stator bore which lie between the abutment slots and the inlet ports. It is necessary to relieve these areas so that the major radius arcuate portion of the rotor cannot form a seal between the slot and the inlet port. If this sealing were allowed to take place small pocketsl would be isolated at the end of the abutments which would become reduced in capacity as the abutment moved inwards thus exerting a heavy pressure tending to sep-arate the abutments from the rotors as represented in Figs. l0 and 11.

In Fig. 12 we have shown the manner of laying out the contour of the roto-r and the proportions for the several curves whereby the ends of the major circular arc and the minor circular arc are interconnected by curves which eiTect a constant rate of acceleration for one half of the movement of the coacting abutment and a constant rate of deceleration for the second half of the movement of the abutment. The proportions have been represented in Fig. l2 and are as follows:

A=Angular length of each circular arc in degrees R=Radius of major circular arc Rm=Radius at 45 degrees toa radial line bisecting either adjacent circular arc RAL=Radius at Lydegrees from end of major cir-` cular arc 1`L=Radiusat L degrees from end of minor circular arc. The following equations govern the 'proportions in which the contours are formed:

We have found the mathematical formula set forth herein highly practicable in producing efcient pump and motor equipment. We realize however, that `modications may be made vand we vdesire that it be understood that ncl limitations upon our invention are intended other than may be imposed by the scope of the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States, islas follows: l 1 1. A device of the class described comprising a casing for fluid including a series of stator chambers, a shaft extending therethrough: a series of rotors phase displaced at degrees on said shaft, there being one rotor `to each chamber aligned with the plane of the respective chamber, a division plate between said chambers, inlet vand outlet passages for directing fluid through `said casing, said division plate, andsaid chambers, diamet'rically disposed slidable abutments extending f from the casing through the stator chambers to-the exterior peripheral face of said rotors, said rotors having their peripheries formed on major and minor circular arcs interconnected end to end on curves which are determined by points locatedaccord- Aing tothe equations: Y

R=Radius of major circular arc 1=Radius of minor circular arc Rm=Radius at 45 degrees to a radial line bisecting either adjacent circular arc RL=Radius at L degrees from end of major circular arc rL=Radius at L degrees from end of minor circular arc L=Distance in degrees from end of major and minor circular arcs.

2. A device of the class described comprising a casing for iiuid including a series cf stator chambers, a shaft extending therethrough, .a series of rotors phasevdisplaced at 90 degrees on said shaft, thereY beingv one rotor to each chamber aligned with the plane of the respective chamber, a division plate between said chambers, inlet and outlet passages for directing of said curve and a constant deceleration path from said mid point of said curve to the other of said arcs Where the mid point of said curve has a radius which is equal to the sum of the radii of 'said major and minor circular arcs divided by two. 3. A' device of theiclass described comprising a casing for fluid includinga series of stator chambers, a shaft extending therethrough,` a series lofrotors phase displaced at 90 degreeson shaft, there beingone rotor to each chamber aligned with the plane ofthe respective chamber, a division plate between said chambers, inlet and outlet passages for directing fluid through said casing, said division plate, and said chambers; diametrically disposed slidable abutments extending from the casing through the stator chambers to the exterior peripheral face of said rotors, said rotors having their peripheres formed on major and minor circular arcs interconnected end to end on a curve having the p0rtion thereof between said major arc and the midpoint of the curve extending in a path for` providing constant radial acceleration for said abutments and the other portion thereof between said mid point and said minor arc extending in a pathiproviding constant radial cle-acceleration fortsaid abutments, said last mentioned portions ofthe said curves being joined at a point disposed-'on a radius equal to the sum of the radii ofk said major and minor circular arcs divided by two.` t

4; A device of the class described comprising a casing for fluid including a series of stator chambers, a shaft extending therethrough, a

se-ries of rotors phase-displaced at degrees on said shaft, there being one rotor to each chamber aligned with the plane of the respective chamber, diametrically opposed slidable abutments extending from the casing throughthe stator chambers to the exterior peripheral face of the rotors, said rotors having their peripheries formed on major and minor circular arcs interconnected end to end on a joining curve having Vone portion thereof extending in a constant radial acceleration path and another portion extending in a constant radial deceleration path, said joining curve being determined so that all radii disposed L degrees from the end of the minor circular arc are` determined by the'equation:

R R www and L0 from the end of the major circular arc is determined by the equation:

R Rm RFR-@T52 wherein CHARLES SCOTT PRENDERGAST. RICHARD SAMUELk PRENDERGAST. GODFREY WILLIAM BEAUMONT DIXEY. HAMILTON GORDON.

from end of major cir- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Balsiger Sept. 3, 1935 Number 

